C85 Stroker (SE00979AT)

[phil123]

For buyers and re builders of C-85 strokers who are led to believe they're getting O-200 HP (up to the maximus of 100 ), here is the description right out of Aircraft Specialty Services STC conversion:

"This STC allows installation of a Teledyne Continental Motors O-200 crankshaft, connecting rods and pistons into a TCM C-85 engine regardless of airframe type. There is no performance change. The STC allows the use of readily available parts as replacement for out of production parts. The STC is Issued on per engine serial number basis. Supplemental data plate included."

Parts Included with C85/0200 Kit - C85-STC-1

(1) 653012 1 New Continental 0200 Crankshaft

(4) AEC530348 New 0200 Pistons

(4) STC Rods - O-200 Yellow tag Rods (overhauled, outright)

(1) C85/O200 STC ONLY - C85-STC C85/0200 STC paperwork


https://www.aircraftspecialties.aero/c8 ... c85-stc-1/

[2066]

Don Swords "pioneered" and earned the "0200 crank STC" back when he was operating Don's Dream Machines & saw need for replacing increasingly scarce C85 cranks. When asked about meaningful HP increase, he said that any "claim" for increased HP would have likely complicated FAA approval of his STC application, significantly. When one of our members pressed him a bit at the Newnan convention (2002), he said "OK, maybe around 92 HP", but qualified that statement with some discussion of how much difference in performance that props, carbs, weight, trim, "cleanliness", mag timing, etc. and etc. can make in any attempt to quantify exact HP increase. Don sold the STC to Aircraft Specialties Services. It's the same STC. I've flown for 14 years behind a majored C85 that was "upgraded(?)" with a new 0200 crank, four new 0200 cylinder assemblies and refurbed 0200 rods. With the same 7150 prop, it cruises well, climbs OK & fuel burn is about the same as before (Stromberg). My C85 performed about the same...best I remember. But, when we spend a LOT of money on most any "upgrade" for our planes, it's awfully easy to "feel" that the money bought increased performance. (In any event, I told Donna that it was a nice "investment" and I'm sticking to that story ) YMMV. Mac

[cdoughty]

Since you mentioned upgrade to Marvel carb I will give my rant/advice on that. Before you invest check out the interwebs for Marvell issues on C-85s. My experience was the problems with midrange mix were real. Marvel doesn't really know anymore, after several acquisitions and moves, how to set up these carbs to run every time on a C-85. When you talk to them you get a lot of "sometimes they just do that" or "we can try X, maybe that will help". Meanwhile you have an airplane with the cowl off and get to spend your time polishing, not flying, while you ship parts back and forth.

So my advice is if you upgrade be prepared for it to not work out of the box. It might because some do, but it might not. If you have one that works, don't send it back as a core for a rebuild--keep your good jets, venturis, etc.and get rewbuilt locally.

[edidin]

If one uses just the ratio of the stroke on the C-85 vs. the O-200 crank/rods, end up with about 92 hp predicted.

IMHO weight reduction is a better tack for a C120 than power increase, since cruise speed is never really going to change in a draggy airplane, but climb rate will with increasing power or decreasing weight.

[6643]

The difference you describe sounds somewhat analogous to how Continental vs. Bendix fuel injections systems meter fuel

Yes, the Marvel mixture control is simply a valve that throttles the fuel going from the bowl into the fuel circuit of the carb.

[nm taildragger]

For buyers and re builders of C-85 strokers who are led to believe they're getting O-200 HP (up to the maximus of 100 ), here is the description right out of Aircraft Specialty Services STC conversion:

"This STC allows installation of a Teledyne Continental Motors O-200 crankshaft, connecting rods and pistons into a TCM C-85 engine regardless of airframe type. There is no performance change. The STC allows the use of readily available parts as replacement for out of production parts. The STC is Issued on per engine serial number basis. Supplemental data plate included."

Parts Included with C85/0200 Kit - C85-STC-1

(1) 653012 1 New Continental 0200 Crankshaft

(4) AEC530348 New 0200 Pistons

(4) STC Rods - O-200 Yellow tag Rods (overhauled, outright)

(1) C85/O200 STC ONLY - C85-STC C85/0200 STC paperwork


https://www.aircraftspecialties.aero/c8 ... c85-stc-1/

Wow... $6K and no bearings or gaskets included? I'm in the wrong business...